Two Bedroom ADU for Family in San Marcos
Roadrunner Road, San Marcos, CA 92078
A family in San Marcos started their ADU journey years before actually getting permits. Why? Because their property included an easement that needed to be ‘vacated’ by the utility so that they could use part of their property. They had to halt their plans for a customized ADU.
But they persisted! And years later, they successfully worked towards a clean title and were ready to revisit the ADU build. But this time? They chose a standard plan and were able to get permits in under 3 months!
Read more about their story: Why One Homeowner Switched from a Custom to Pre-Approved ADU
Floor Plan:
2BR/1BA 28×27 Square
Community:
The San Marcos ADU Guide
SnapADU is proud to have been selected by the City of San Marcos through a competitive bid process to design the City’s pre-approved ADU plans. This experience has given our team a deep understanding of San Marcos ADU regulations, permitting requirements, and development standards.
One of the most unique aspects of building an ADU in San Marcos is the Community Facilities District (CFD) process, commonly known as Mello-Roos. Depending on the property location, homeowners may need to annex into an existing CFD or pay an in-lieu fee as part of the development process. This requirement can add several months to a project’s timeline and is often one of the biggest surprises homeowners encounter.
San Marcos also has several development standards that differ from neighboring jurisdictions. Detached ADUs are generally limited to 1,000 square feet, and the city requires a 10′ building separation between between the primary residence and detached ADU. Additionally, ADUs are expected to be architecturally compatible with the primary residence, making exterior design coordination an important part of the planning process.
San Marcos ADU Permitting
Most ADU permits in San Marcos are approved within approximately 5 to 7 months after submission, although timelines vary depending on project complexity and whether CFD processing is required.
Permit costs are moderate, generally range from approximately $10-14/sqft, depending on project size and scope. The City accepts digital permit submissions, which helps streamline portions of the review process.
One unique requirement in San Marcos is the building verification survey and setback certification process for detached ADUs. These surveys confirm that the ADU is being constructed in the approved location and complies with setback requirements before inspections can proceed.
As of May 2025, San Marcos no longer requires soils reports for most ADU projects. A soils investigation is generally only required when grading is proposed or if site conditions identified during construction warrant additional geotechnical review.
San Marcos Pre-Approved ADU Plans
San Marcos offers a library of pre-approved ADU plans designed to help homeowners reduce upfront design costs and simplify the permitting process.
SnapADU was selected by the City through a competitive process to design these plans, which were created to balance efficient permitting, construction affordability, and high-quality design. The plans provide homeowners with a proven starting point while still requiring site-specific review to address grading, utilities, setbacks, and other property conditions.
While pre-approved plans can reduce design time and create greater predictability, homeowners should understand that every property is unique. Many homeowners ultimately choose between pre-approved, standard, semi-custom, and fully custom plans depending on their goals, budget, and desired level of customization. Learn more about pre-approved ADU plans.
